1. Preheat oven to 400F. Line two standard baking sheets with parchment
paper or silicone baking mats. In a medium bowl, whisk together flour,
cocoa powder, cream of tartar, baking soda, salt, 1 teaspoon cinnamon,
and ¼ teaspoon ground chipotle chile.
2. In the bowl of an electric mixer, beat butter and 1 ½ cups sugar on
medium speed until pale and fluff, about 3 to 4 minutes. Add eggs, one
at a time, scraping down the sides of the bowl as needed. Add vanilla
and beat to combine. Reduce speed to low and add flour mixture, beat to
combine.
3. In a small bowl, combine remaining ¼ cup sugar, 1 teaspoon cinnamon,
and ¼ teaspoon ground chipotle. Form heaping tablespoons of dough into
balls and roll in cinnamon sugar mixture. Place on prepared baking
sheets, spacing 3 inches apart. Bake, rotating sheets halfway through,
until cookies are set in center and begin to crack, about 10 minutes.
Let cookies cool on sheets for 5 minutes before transferring cookies to
wire racks to cool completely.